HELP with science project

I NEED HELP PLS.
I am a 13-year-old student with an ambitious science fair project and I've
got a problem. In my science fair project I'm trying to see if a certain
substance can be harmful to fruit flies. To determine that the substance
did clog the spiricals, I had to do histological sectioning. After
looking at the slides and taking pictures, I ran into the problem of
determining if the tubular structures I was seeing underneath the
microscope were spiricals or intestines. How can I tell the difference
between the two. I would also appreciate any information on how to get
oriented with the body of the fruit fly under the microscope. Thank you
very much for any help you could provide.
Sean Tabacsko
Center for the Arts and Sciences, Saginaw, MI
hockeyst at cris.com